The invention relates to a rotating connector for the transfer of at least one pressurized processed fluid, and comprising a central stem on which there is placed a number of ring elements comprising at least one annulus element for fluid transfer between an associated course in the stem and an outlet from the connector, and a bearing ring element arranged on each side of the annulus element, which bearing ring element is provided with bearings for abutment against adjacent ring elements and is sealed against the ring elements by dynamic seals operated by a barrier liquid having a higher pressure than the process fluid pressure, and a locking nut to keep the ring elements preloaded against a holding member on the stem.
A rotating connector or swivel of the above-mentioned type is particularly used within the offshore industry, for the transfer of process fluids and injection of gas and water in connection with recovery and processing of oil and gas. In such a connector a number of ring elements, with bearings and seals, normally will be placed above each other on the central stem. The locking nut arranged at the top of the stem keeps all the rings prestressed or preloaded against a shoulder on the stem. During the assembly of the connector or swivel, the ring elements are preloaded against the shoulder by means of the locking nut and a preloading tool.
The dynamic seals of the connector during operation are activated by a hydraulic barrier liquid having a pressure which is always higher than the process fluid pressure in the individual dual main courses in the swivel. In this manner process liquid is prevented from leaking across the seals, at the same time as the seals are activated by a clean hydraulic oil, so that the seals operate under very favourable conditions.
However, when barrier liquid pressure is applied, the stem will stretch and the locking nut will be twisted because of the operating piston forces. This will also be able to entail that the roller bearings lose their preload. These circumstances will result in an undesirable increase of the extrusion openings for the individual dynamic seals, and the bearing ring elements are also given a greater possibility for deformation under varying operational conditions. It is obviously desirable to avoid that this stem extension and/or deformations of the rings assert themselves in the sealing zone.
The object of the invention therefore is to provide a means which maintains the preload on the roller bearings and thereby reduces the possibility of the bearing ring elements for deformation, and which further eliminates/restricts changes in the extrusion openings for the dynamic seals, so that the operational conditions for these critical seals are substantially improved.
The above-mentioned object is achieved with a rotating connector of the introductorily stated type which, according to the invention, is characterized in that it is provided with a compensating unit in the form of a piston means placed between the locking nut and an adjacent ring element on the stem, and which is arranged to be activated by a hydraulic pressure fluid, so that a preload on the ring elements and the bearings is maintained during operation of the connector.